NEW YORK — Union Pacific Corp, the No. 1 U.S. railroad, said on Wednesday that a key measure of performance would come in better than expected for 2018, sending shares up 1.6 percent in after-hours trade. The Omaha, Nebraska-based company said its operating ratio was expected to be 62.7 percent for 2018, a 0.1 point improvement from 2017 after stronger-than-expected international container imports and cost controls bolstered results.